Silver alloys



- SILVER ALLOYS Maximilian Stand, Bronx, N.Y., assignor to The Ventureglorporation, Bloomfield, N.J., a corporation of New ersey No Drawing.Filed Aug. 26, 1958, Ser. No. 757,199

3; Claims. (Cl. 75-173) This invention relates to metal allo and, inparticular, to novel silver alloys and'to new and improvedmethods fortheir production.

By reason of its color and excellent electrical and thermal properties,silver is a very desirable metal'for many industrial applications. Itsuse is often restricted,

. however, because of its inherently poor mechanical properties, and, inparticular, its low tensile strength, hardness properties andcharacteristics of pure or relatively pure silver, would also presentimproved physical properties and at least equivalent electricalproperties. Such alloys have not, however, proved entirely satisfactory.Often, when satisfactory physical characteristics such as tensilestrength and elasticity have been obtained, the resulting alloy provesto be inferior with respect to color, thermal and electrical properties,or tarnish resistance. For example, while silver has been alloyed withmany other metals in an attempt to solve the foregoing problems, withthe result that some of its mechanical properties have been improved inthe resulting alloys, the alloying usually results in a substantiallylower electrical conductivity, i.e., a decreased current-carryingcapacity, and these alloys tend to fail for the same reasons as finesilver provided service conditions are too severe.

Apart from direct alloying applications, other attempts at solving theinherent disadvantages of pure silver as a contact material have beenmade through use of powder metallurgical techniques. Thus, refractorymetals such as tungsten, or certain oxides such as cadmium oxides, havebeen sintered with silver. While these sintered contact materialsprovide a very high resistance to sticking or welding and are erosion,their electrical and thermal conductivity is considerably lower thanthat of pure silver. In addition these products have a tendency towork-harden and their industrial applications are extremely limited forthis reason.

It is an object of the present invention to provide new silver alloyshaving substantially the color of pure silver and other desirableinherent properties of silver, but which are characterized by superiorcorrosion and tarnish resistance as well as improved mechanicalproperties and extreme resistance to are erosion, welding and sticking.

A further object of the invention is the provision of novel methods forthe production of homogeneous silver alloys possessing theaforementioned improved physical, thermal and electrical properties.

In general, the alloys of the present invention comprise a majorproportion of silver with smaller proportions 2,944,892 Patented July12, 1960 Component Percentage by Weight Not less than per: 9- Vanadium0.01 1.0%.

Specifically, I have found that an alloy having optimum properties forelectrical contact applications is obtained in accordance with myinvention when the final composition consists essentially of parts byweight silver, 10 parts by weight copper, and 0.5 part by weightvanadium.

The resulting alloys are ductile, and may be cast, drawn, rolled orformed by any method commonly used in metalworking. The alloys do notwork-harden, and have a superior corrosion and tarnish resistance aswell as' generally improved merchanical properties. The alloys of theinvention are useful for virtually all electrical applications, such asfor slip rings, commutators, etc. In

addition, there are numerous other non-electrical industrialapplications for which the alloys are ideally suited.

' the melting point of vanadium must be exceeded considerably. Thisincreases the danger of loss of silver due to volatilization, however,and, accordingly, I have found that pro-alloying is essential to properpractice of the invention.

The copper and vanadium are melted together in the ratio required forthe final alloy, or in the ratio forming a eutectic mixture in order totake advantage of a lowered melting temperature. In this case,additional copper, as required, is added to the silver in the finalalloying step to obtain the required ratio.

The copper-vanadium pre-alloy, as well as the final silver alloy aremelted under a reducing atmosphere and then re-cast in order toeliminate all gas inclusions. For applications requiring extremely highelectrical and thermal conductivity, the silver alloy preferably isproduced within a vacuum furnace.

The foregoing as well as other features and objects of the invention maybe best understood by reference to the following specific examples oftypical alloys prepared in accordance with my invention:

Example I A master alloy was prepared by melting 1000 grams of copperand 50 grams of vanadium in an induction furnance with a boric acidflux. In order to insure good solution of the vanadium in the copper,the melting point of vanadium was exceeded by heating the melt to justbelow 2000 C.

The copper-vanadium pro-alloy, in amount grams, was melted with 895grams of silver in the presence of a cover of burning natural gas.

The resulting alloy (prepared under reducing atmosphere) had aconductivity of 75% IACS and a hardness of M92 (Rockwell). An alloy ofthe same proportions was prepared within a vacuum furnace and it wasfound that the conductivity was increased substantially.

Example 11 A master alloy prepared in accordance with the procedure ofExample I, but comprised of 1000 grams of copper and 100 grams ofvanadium, was melted with 890 grams of silver; the vanadium-copper alloybeing employed in amount of 108 grams.

Upon subsequent testing of this alloy, it was found that itsconductivity was higher than the alloy of Example .1. Vacuum meltingimproved the conductivity of this type alloy even more. The hardness,however, was lower than that demonstrated by the alloy of Example I.

7 Example III N A pre-alloy of copper and vanadium was prepared -from900 grams of copper and 100 gramsrof vanadium.

The pro-alloy, in amount 100 grams, was melted with 900 grams of silver.W

Upon subsequent testing, it was found that this alloy demonstratedsuperior hardness, but lower conductivity,

. than the alloys of Examples I and II.

The following tabulated examples illustrate additional alloycompositions produced in accordance with the invention which possess thesame desirable properties set forth hereinbefore:

:Example N I IV V VI VII Silver (parts) 89.00 89. 50 89.75 80. 99

. Copper (parts) 1000 10.00 10.00 10.00 Vanadium (parts) 1.0 0.60 0.250.01

This application constitutes a continuation-in-part replacement of myformer copending application Senial No. 656,193, filed May 1, 1957, nowabandoned, and also entitled Silver Alloys.

1 claim: 1. An homogeneous silver alloy consisting of the fol- 4 lowingingredients within the respective ranges indicated based on percentagesby weight:

Silver Not less than Copper 9-19%. Vanadium 0.01-1.0%.

2. An homogeneous silver alloy having substantially the color of puresilver, said alloy being characterized, as compared with pure silver, byimproved mechanical properties, and being more resistant to staining,corrosion, and tarnishing, and demonstrating superior resistance to areerosion, welding and sticking when empolyed as a contact material withinelectrical circuitry consisting of the following ingredients within therespective ranges indicated based on percentages by Weight:

Silver Not less than 80%. Copper 9-19%. Vanadium 0.011.0%.

Silver .Copper l0 'Vanadium 0.5

References Cited in the file of this patent UNITED STATES PATENTS1,612,782 Vogt et a1 Dec. 28, 1926 1,614,752 Mitchell Ian. 18, 19272,830,898 Gwyn Apr. 15, 1958 FOREIGN PATENTS 706,248 Germany May 21,1941

1. AN HOMOGENEOUS SILVER ALLOY CONSISTING OF THE FOLLOWING INGREDIENTSWITHIN THE RESPECTIVE RANGES INDICATED BASED ON PERCENTAGES BY WEIGHT:SILVER NOT LESS THAN 80%. COPPER 9-19%. VANADIUM 0.01-1.0%.